Advertisements
Advertisements
Question
The electric field at a point associated with a light wave is `E = (100 "Vm"^-1) sin [(3.0 xx 10^15 "s"^-1)t] sin [(6.0 xx 10^15 "s"^-1)t]`.If this light falls on a metal surface with a work function of 2.0 eV, what will be the maximum kinetic energy of the photoelectrons?
(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)
Advertisements
Solution
Given :-
`E = 100 sin [(3 xx 10^-15 "s"^-1)t] sin [(6 xx 10^-15 "s"^-1)t]`
= `100 xx 1/2 cos [(9 xx 10^15 "s"^-1)t] - cos[(3 xx 10^15 "s"^-1)t]`
The values of angular frequency `ω` are `9 xx 10^15` and `3 xx 10^15`.
Work function of the metal surface, `phi = 2 "eV"`
Maximum frequency,
`v = ω_(max)/(2pi) = (9 xx 10^15)/(2pi) Hz`
From Einstein's photoelectric equation, kinetic energy,
K = hv - `phi`
`⇒ K = 6.63 xx 10^-34 xx (9 xx 10^15)/(2pi) xx 1/(1.6 xx 10^-19) - 2 "eV"`
⇒ K = 3.938 eV
APPEARS IN
RELATED QUESTIONS
The work function for a certain metal is 4.2 eV. Will this metal give photoelectric emission for incident radiation of wavelength 330 nm?
Plot a graph showing the variation of photoelectric current with collector plate potential at a given frequency but for two different intensities I1 and I2, where I2 > I1.
point out any two characteristic properties of photons on which Einstein’s photoelectric equation is based ?
Briefly explain the three observed features which can be explained by Einstein’s photoelectric equation.
Define the terms (i) ‘cut-off voltage’ and (ii) ‘threshold frequency’ in relation to the phenomenon of photoelectric effect.
Using Einstein’s photoelectric equation shows how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.
A non-monochromatic light is used in an experiment on photoelectric effect. The stopping potential
Consider the situation of the previous problem. Consider the faster electron emitted parallel to the large metal plate. Find the displacement of this electron parallel to its initial velocity before it strikes the large metal plate.
(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)
Use Einstein’s photoelectric equation to show how from this graph,
(i) Threshold frequency, and (ii) Planck’s constant can be determined.
How does one explain the emission of electrons from a photosensitive surface with the help of Einstein’s photoelectric equation?
Choose the correct answer from given options
Photons of frequency v are incident on the surface of two metals A and B of threshold frequency 3/4 v and 2/3 v, respectively. The ratio of maximum kinetic energy of electrons emitted from A to that from B is
Each photon has the same speed but different ______.
- In the explanation of photo electric effect, we assume one photon of frequency ν collides with an electron and transfers its energy. This leads to the equation for the maximum energy Emax of the emitted electron as Emax = hν – φ0 where φ0 is the work function of the metal. If an electron absorbs 2 photons (each of frequency ν) what will be the maximum energy for the emitted electron?
- Why is this fact (two photon absorption) not taken into consideration in our discussion of the stopping potential?
There are materials which absorb photons of shorter wavelength and emit photons of longer wavelength. Can there be stable substances which absorb photons of larger wavelength and emit light of shorter wavelength.
The photon emitted during the de-excitation from the first excited level to the ground state of a hydrogen atom is used to irradiate a photocathode in which the stopping potential is 5 V. Calculate the work function of the cathode used.
